Evolution of stresses in metal injection molding parts during sintering
(1. Institute for Advanced Materials and Technologies,
University of Science and Technology Beijing, Beijing 100083, China;
2. State Key Laboratory for Advanced Metal and Materials,
University of Science and Technology Beijing, Beijing 100083, China)
University of Science and Technology Beijing, Beijing 100083, China;
2. State Key Laboratory for Advanced Metal and Materials,
University of Science and Technology Beijing, Beijing 100083, China)
Abstract: The evolution of stresses due to inhomogeneity in metal injection molding (MIM) parts during sintering was investigated. The sintering model of porous materials during densification process was developed based on the continuum mechanics and thermal elasto-viscoplastic constitutive law. Model parameters were identified from the dilatometer sintering experiment. The real density distribution of green body was measured by X-ray computed tomography (CT), which was regarded as the initial condition of sintering model. Numerical calculation of the above sintering model was carried out with the finite element software Abaqus, through the user-defined material mechanical behavior (UMAT). The calculation results showed that shrinkages of low density regions were faster than those of high density regions during sintering, which led to internal stresses. Compressive stresses existed in high density regions and tensile stresses existed in low density regions. The densification of local regions depended on not only the initial density, but also the evolution of stresses during the sintering stage.
Key words: metal injection molding; CT detection; sintering; densification; stress; numerical simulation